In one Internet newsgroup, someone else asked why there are three terminals on the battery, and one responder said that the third terminal was perhaps there to measure the temperature of the battery during recharging. I came across a battery that has almost exactly the same dimensions and appearance as the battery in my Zaurus, but the polarity is reversed.

If the battery you are considering is a Lithium Ion then the 3.6/3.7 is probably just a matter of rounding rather than a real difference. If it were me though I'd probably just stick with a pack of AAA NiMH batteries and a conector for the back of the Z.

is my calculation correct?i'll pack 5 batteries of 1.2v each to the back connector: 5x1.2=6vand i need no more current adjustments.

is that so?

Sounds about right. I don't have a Z yet but assuming it's a 5V DC supply that should work. I think I saw someone else mention doing this on this board in the past week so you might want to search a bit. You'll need to have the batteries in series and make sure you get the polarity right (most devices are center-positive but check your existing charger to be sure. If you can afford the space I'd use AA instead of AAA.

6v will fry the recharge circutry in the Z. Use 4 rechargable batteres *ONLY* for 4.8 v. Don't use 4x1.5 v alkalines either - they would probably sag under the 5.25v (Or whatever the limit is. It isn't much above 5) but the initial surge would do not nice things to the Z.

4 nickle metal hydride rechargable AA work fine. I've had my 5500 running for over 20hrs straight of of them. (New 2200mah batteries I bought for ~$15 Canadian for 4, Energizer, I think.)